Headsets are used as loudspeakers to listen to sound produced by a wide variety of electronic audio devices. Examples of such devices that are used with a headset are a broadcast radio receiver, a CD Player, an MP3 player, two way radio, mobile phone and television receiver. A headset can be connected to the audio device by a cable or with a wireless connection such as Bluetooth, DECT, or another wireless technology. Wireless connections can be used to free the user from being tied directly to the audio device by a cable. A headset typically includes an audio transducer worn close to the ear. In case the headset provides audio for both ears, the headset has a pair of transducers, one for each ear. The headset also includes any additional electronics required to connect the headset to the audio device the user wishes to listen to, and optionally, additional user interface (UI) features such as a volume control. In case of a wireless headset, a battery, a solar cell or another power source is required to power the headset. A headset may also include electronics used to modify sound by the means of DSP (Digital Signal Processing).
Typical headsets use conventional loudspeakers utilizing normal air conduction by exciting pressure waves in the volume of tympanic canal, which waves travel along the canal and ultimately excite the tympanic membrane producing sensation of hearing. A well-known headphone type based on air conduction principle is placed over the ear and transmits sound to the user via the air canal. Microphones are correspondingly based on the  detection of pressure changes or pressure gradients. Especially in loudspeakers this technology results in relatively low efficiency and, hence, in relatively high power consumption. Moreover, these headsets are adversely affected by the ambient noise. In addition to the low-efficiency of loudspeakers, another matter reducing the efficiency significantly is the air-tissue interface at the tympanic membrane. This interface is not ideal, and further gains in efficiency may be achieved by not going to the pressure domain at all.
It is further known to use bone conduction to transmit the sound, whereby especially the background noise can be reduced. U.S. Pat. No. 6,408,081 B1 discloses a bone conduction voice sound transmitting apparatus including an earpiece that is adapted for insertion into the external auditory canal of a user, the earpiece having both a bone conduction sensor and an air conduction sensor. The bone conduction sensor is adapted to contact a portion of the external auditory canal to convert bone vibrations of voice sound information into electrical signals. The air conduction sensor resides within the auditory canal and converts air vibrations of the voice sound information into electrical signals. The voice sound transmitting apparatus also includes a speech processor and transmitter. The speech processor samples the output from the bone conduction sensor and the air conduction sensor. In comparing the sampled output, the speech processor is able to filter noise and select the pure voice sound signal for transmission. The transmission of the voice sound signal may be through a wireless linkage. In addition, the bone conduction sensor and the air conduction sensor are preferably designed so as not to occlude the external auditory canal. The apparatus in U.S. Pat. No. 6,408,081 B1 may also be equipped with a speaker and receiver to enable two-way communication. The voice sound transmitting unit further includes a casing having an ear attachment portion and a fitting portion that connects the ear attachment portion with the bone conduction sensor and the air conduction sensor. The ear attachment portion is contoured to fit over and behind the upper ear lobe of the user and is preferably made of a lightweight aluminium or plastic material. It can be appreciated that the primary purpose of the ear attachment portion is to secure the voice sound transmitting unit in proper position. The fitting portion is integral with the ear attachment portion. The voice sound transmitting apparatus is fit so that the bone conduction sensor is in contact with a portion of the external auditory canal. The bone conduction sensor rests against the posterior superior wall of the external auditory canal, with the fitting portion shaped to bias the bone conduction sensor into position. 
The apparatus in U.S. Pat. No. 6,408,081 B1 is relatively uncomfortable in use, especially due to the hard material of the ear attachment portion. Further, it is relatively difficult to insert the apparatus into the right position, and relatively much energy is required in order to achieve a enough strong impact to excite a bone.